1. Field of the Invention
This invention relates to coal feed locks and more particularly to apparatus for supplying coal to high pressure gas producers.
2. Description of the Prior Art
Typically, conventional coal feed locks for delivering coal to high pressure gas producers or gasifiers employ sealable transfer chambers. In operation, the coal is dropped or otherwise loaded into the transfer chamber and the chamber is then sealed from the atmosphere. The chamber is then placed in communication with the high pressure gas producer and the coal is allowed to flow into the gas producer.
Conventional coal feed locks of the type described suffer a number of important disadvantages which greatly limit their usefulness. Perhaps the most important disadvantage is that such locks permit large volumes of high pressure gas to escape to the atmosphere. The high pressure gas can escape in several ways. For example, gas may simply leak through the various seals of the lock. More importantly, each time a measured amount of coal is transferred to the gas producer, the transfer chamber fills with high pressure gas. This gas is released to the atmosphere prior to or during the refilling of the transfer chamber with coal and thus is lost.
Additionally, prior art coal locks require large amounts of head room. Further, since very high pressures are involved, the moving parts of these coal locks tend to become unbalanced, causing excessive wear and resulting in increased high pressure gas loss and increased maintenance costs.
A number of prior art devices exist that can deliver metered portions of a material from a bulk supply of the material. Examples of such prior art devices can be found in the following U.S. Pat. Nos. 2,893,609; 2,914,223; 3,172,578; 3,394,850; 3,794,234.